HSC Survey Results

German Bank Survey # 4 Results from 25/09/2022

Survey Details

9 commercial purse seiners conducted this fishing survey on 25/09/2022 starting at 20:00:00.

9 vessels ran two transects in the German Bank box and one transect in the Seal Island Box.

There was a plankton tow and replicate conducted and CTD cast by Lady Janice II.

A total of 1,657 tags were applied during the survey over 7 events from 2022-09-27 to 2022-09-29, from 3 vessels.

Samples were obtained for target strength estimation.

Tides Tables

Tide Schedule for Yarmouth NS, Station #365, Source: www.waterlevels.gc.ca

Acoustic Equipment

Each vessel was equipped with a Simrad ES38-18/200-18C combi (2-in-1) transducer prior to the survey that contains a 38kHz split beam and 200 kHz single beam transducer. Data was logged to the computer hard-drive for post-processing. All participating boats were calibrated on 38kHz before the survey.

Survey Results

Main Results

The results are subject to change as DFO will re-evaluate data editing, area estimation and apply a target strength.

Preliminary biomass prediction for German Bank using standardized parallel transects is 62,399mt, and with turnover 60,778mt. The preliminary biomass estimate for Seal Island is 6,134mt.

Transect Details

Table 1: Transect Details
Vessel Transect # Date/Time Start Date/Time End Start Lon Start Lat End Lon End Lat Location Distance (km) Speed
BP T01 2022-09-25 19:55:04 2022-09-25 22:19:06 -66.478 43.566 -66.478 43.234 GB 36.96 8.31
BP T02 2022-09-25 22:59:05 2022-09-26 01:15:04 -66.344 43.234 -66.344 43.565 GB 36.94 8.80
BP T03 2022-09-26 02:08:05 2022-09-26 03:53:07 -66.215 43.500 -66.217 43.250 GB 27.81 8.58
C1 T01 2022-09-25 19:53:34 2022-09-25 22:18:44 -66.495 43.569 -66.496 43.234 GB 40.59 9.06
C1 T02 2022-09-25 22:57:19 2022-09-26 01:17:56 -66.359 43.235 -66.358 43.566 GB 39.74 9.16
C1 T03 2022-09-26 01:56:07 2022-09-26 03:45:58 -66.230 43.502 -66.229 43.245 GB 30.74 9.07
FM T01 2022-09-26 20:47:40 2022-09-26 23:19:34 -66.389 43.567 -66.389 43.233 GB 38.43 8.20
FM T02 2022-09-26 23:56:41 2022-09-27 02:20:15 -66.256 43.235 -66.255 43.568 GB 37.97 8.57
FM T03 2022-09-27 03:00:00 2022-09-27 04:48:59 -66.137 43.499 -66.138 43.246 GB 29.13 8.66
LB T01 2022-09-25 19:52:19 2022-09-25 22:34:14 -66.434 43.567 -66.434 43.233 GB 38.51 7.71
LB T02 2022-09-25 23:18:05 2022-09-26 01:32:55 -66.299 43.233 -66.300 43.566 GB 37.84 9.09
LB T03 2022-09-26 02:15:32 2022-09-26 04:02:30 -66.177 43.505 -66.178 43.247 GB 29.42 8.91
LJ T01 2022-09-25 19:58:03 2022-09-25 22:22:24 -66.374 43.565 -66.374 43.233 GB 36.96 8.30
LJ T02 2022-09-25 23:01:26 2022-09-26 01:21:27 -66.240 43.234 -66.240 43.567 GB 37.07 8.58
LJ T03 2022-09-26 01:59:03 2022-09-26 03:52:12 -66.125 43.503 -66.125 43.247 GB 28.66 8.21
LM T01 2022-09-25 19:51:45 2022-09-25 22:21:21 -66.448 43.568 -66.448 43.233 GB 38.00 8.23
LM T02 2022-09-25 23:00:18 2022-09-26 01:21:43 -66.315 43.232 -66.314 43.566 GB 37.77 8.65
LM T03 2022-09-26 02:00:23 2022-09-26 03:57:55 -66.190 43.503 -66.190 43.247 GB 29.07 8.01
MS T01 2022-09-25 19:58:45 2022-09-25 22:36:33 -66.464 43.566 -66.463 43.232 GB 39.78 8.17
MS T02 2022-09-25 23:20:50 2022-09-26 01:45:56 -66.328 43.235 -66.329 43.567 GB 39.46 8.81
MS T03 2022-09-26 02:29:55 2022-09-26 04:18:09 -66.203 43.501 -66.204 43.247 GB 29.76 8.91
TM T01 2022-09-25 19:54:06 2022-09-25 22:26:50 -66.418 43.568 -66.419 43.234 GB 37.22 7.89
TM T02 2022-09-25 23:07:21 2022-09-26 01:29:47 -66.286 43.234 -66.284 43.569 GB 37.27 8.48
TM T03 2022-09-26 02:11:40 2022-09-26 03:57:01 -66.164 43.498 -66.165 43.248 GB 27.82 8.55

Survey Summary

Table 2: Acoustic Survey Results
Vessel Transect No.  Target Strength (db/kg) Mean Sa (/m2) Biomass Density (kg/m2)
LJ T02 -35.5 -47.316 0.066
LB T03 -35.5 -48.442 0.051
FM T01 -35.5 -48.770 0.047
LB T01 -35.5 -50.471 0.032
LM T02 -35.5 -50.691 0.030
BP T02 -35.5 -51.135 0.027
LB T02 -35.5 -51.637 0.024
LJ T01 -35.5 -52.227 0.021
MS T03 -35.5 -52.478 0.020
LM T03 -35.5 -52.742 0.019
BP T03 -35.5 -54.086 0.014
LM T01 -35.5 -54.260 0.013
BP T01 -35.5 -54.302 0.013
FM T03 -35.5 -54.387 0.013
C1 T03 -35.5 -54.883 0.012
MS T02 -35.5 -55.117 0.011
FM T02 -35.5 -55.363 0.010
MS T01 -35.5 -55.820 0.009
C1 T01 -35.5 -55.918 0.009
LJ T03 -35.5 -56.095 0.009
C1 T02 -35.5 -56.504 0.008
TM T01 -35.5 -57.186 0.007
TM T03 -35.5 -57.531 0.006
TM T02 -35.5 -58.278 0.005
Note:
Transects are listed from greatest to least backscatter.
Table 3: Survey Summary Table
Layer Target Strength Area (km2) Mean Sa Density (kg/m2) Biomass (tons) Percent Area Percent Biomass Standard Error (tons) Standard Error (%)
German Bank -35.5 800 -52.3349 0.0209 16,580.586 NA NA 3,338.88 20.14
Seal Island -35.5 280 -52.9511 0.0179 5,035.575 NA NA 1,394.58 27.69
School Survey NA NA NA NA NA NA NA NA NA

Greatest Backscatter

A snip from the transect with the greatest backscatter

A snip from the transect with the greatest backscatter

The largest backscatter was seen by LJ, at the following location:

Annual Summaries

Table 4: Annual Comparison Table
Current Year
Previous Year
Ground Survey Number Survey Date HSC Estimate HSC Turnover Adjusted Survey Date HSC Estimate HSC Turnover Adjusted DFO Estimate DFO Turnover Adjusted
German Bank 1 2022-08-14 7,352 7,352 2021-08-23 8,338 8,338 7,460 7,460
German Bank 2 2022-08-28 4,659 3,225 2021-09-05 40,319 38,551 48,023 46,442
German Bank 3 2022-09-11 7,452 6,279 2021-09-20 80,644 73,120 80,447 71,574
German Bank 4 2022-09-25 62,399 60,778 2021-10-05 15,722 461 4,280 0
German Bank 5 2022-10-10 NA NA 2021-10-18 3,113 0 3,805 145
German Bank 6 2022-10-23 NA NA 2021-11-02 12,320 11,197 10,777 10,009
Table 5: Annual Summary Table
Year Ground HSC Estimate HSC Turnover Adjusted DFO Estimate DFO Turnover Adjusted
2021 German Bank 160,456 131,667 154,792 135,630
2022 German Bank NA NA NA NA

Tagging, Plankton, and CTD Data

Tag Data

Vessel Tags
Lady Melissa 248
Sealife II 466
Tasha Marie 943

Plankton Data

Tow Summary Table

Tow 1
Tow 2
Base Details
Vessel Lady Janice II Lady Janice II
Set Number GB2022-06 GB2022-07
Ground GB GB
Date 25/09/2022 25/09/2022
Wind Direction (km/h) S S
Swell (m) 1 1
Air Temp (c) 15 15
Tow Details
Tow Start 18:57:00 19:12:00
Tow End 19:07:00 19:22:00
Start Lat 43.56967 43.56067
End Lat 43.56333 43.56767
Start Lon -66.35667 -66.36100
End Lon -66.35800 -66.36317
Avg Tow Depth (m) 1.68 2.42
Speed NA NA
Heading 187 347
Tide Direction against with
Other Data Collection
Flow Start 167750 189732
Flow End 189732 224990
No. Revolutions 21982 35258
Distance (m) 590.72 947.49
Volume 1855.81 2976.62
Secchi Disappear (m) NA NA
Secchi Reappear (m) NA NA

Tow Depth Profiles

Plankton tow depth profile #1

Plankton tow depth profile #1

Plankton tow depth profile #2

Plankton tow depth profile #2

The first tow is GB2022-06, which was against the tide and had an average depth of 1.68m. The second tow is GB2022-07, which was with the tide and had an average depth of 2.42m.

Captured plankton

Captured plankton from the surface tows

Captured plankton from the surface tows

CTD Data

CTD depth profiles for all 2022 German Bank surveys so far.

Sea surface temperatures

Annual average sea surface temperatures (SST) for German Bank.

Vessel Performance

Speed

Average vessel speed was 8.54. This is above the 8 knot requirement; vessels are urged to slow down to prevent backscatter noise from interfering with the acoustic data.

Distance

More than 2km of distance was cut from the planned lines; vessels are reminded to complete their assigned lines straight and without deviating or cutting corners short.